1. Field of the Invention
This invention relates to a wireless LAN antenna with a single loop for use in radio communication and more particularly to a wireless LAN antenna printed on a dielectric board without needing to be impedance matched by outer components.
2. Description of the Prior Art
Nowadays, wireless communication is more and more popular, since a wireless device has the advantages of portability, so that a user need not be confined by his (or her) location. Thus, one can obtain information or communicate with others anywhere. The difference between wired and wireless communications is that a wireless device has a transmitting and receiving portion and further an antenna for performing wireless signal communication. In the conventional wireless device, the antenna is mainly a dipole which is formed by a metal rod or a helical cylinder, and is extended out from a wireless device. Because compactness has become a new trend for a wireless device, in recent years, the design of an antenna has been improved greatly. At first, the size of an antenna is minimized. However, the antenna has the drawbacks that the antenna itself has enlarged the size of the device. The antenna is extended out from the device and thus easy to pierce the body of the user. Further, it is easily broken. To overcome the drawbacks, a foldable antenna is invented. In general, this antenna can be hidden within the housing of the device. If it is used, the user draws the antenna from the housing. This has resolved some of the aforementioned problems, but it is inconvenient to the user. Therefore, recently, a novel design has been disclosed. The concept of patch antennas has been employed in the antenna design. This type of antenna is so-called "printed circuit antenna". Print circuit antennas have been utilized in the field of radio communications to provide a light weight antenna. U.S. Pat. No. 5,495,260 to couture is an example of a simple dipole antenna realized in the form of a print circuit antenna. U.S. Pat. No. 4,758,843 to Agrawal shows a planar printed circuit substrate having a plurality of dipole antennas and a feed network including a sum and difference hybrid printed circuit thereon. U.S. Pat. No. 5,206,657 to Downey shows a printed circuit radio frequency antenna comprising a pair of double sided printed circuit boards spaced apart by standoffs.
An antenna with high directivity has always been desired for its efficiency in direct point-to-point radio communication. It will be very useful in radio communication to have a printed circuit antenna with high directivity. In addition to its light weight, a planar printed circuit antenna has an advantage that it can be formed at the same time and on the same substrate with other circuit sections. The wireless transceiver system can use this feature to make an integrated system on a printed circuit board to reduce the manufacturing time and cost. The absence of mechanical structures or connectors in the antenna construction also improves the reliability of the wireless transceiver system.
Unfortunately, the existing printed circuit antennas in various configurations do not provide a simple solution for the high directivity antenna. There is a need to develop a printed circuit antenna which has a planar structure to be integrated with other electronic circuits, exhibits higher directivity than a single dipole antenna, and occupies relatively smaller area on the substrate.